On January 10, 1991, petitioner, Robert McKinley, suffered an attack of acute ventricular tachycardia which he contended arose out of and in the course of his employment as an operating engineer at WJLA Television. He claimed that his attack was precipitated by the interaction of employment-induced stress with his pre-existing cardiac condition, hypertrophic cardiomyopathy, a congenital condition. A hearing examiner for the Department of Employment Services (“the agency”) denied his claim for temporary total disability under the District of Columbia Workers’ Compensation Act of 1979, D.C.Code §§ 36-301 et. seq. (1993 Repl.) (“the Act”), on the ground that he did not sustain an injury which arose out of and in the course of his employment. We affirm.
FACTUAL SUMMARY
In Fall 1984, Mr. McKinley discovered that he had a congenital heart condition, diagnosed as hypertrophic cardiomyopathy/ven-tricular tachycardia. In Spring 1985, and again in June 1986, he underwent cardiac medication tests to determine the most effective medication for his condition. The 1986 tests took place at the National Institutes of Health (NIH) where ventricular tachycardia (V-tach) was induced. During the tests, he went into cardiac arrest and, as Mr. McKinley explained, the doctors “used the electro padels to bring me back.” He described this incident as “a very difficult experience, very traumatic.” In May 1990, Mr. McKinley experienced heart palpitations, and was monitored by way of a holter. The results of the holter monitor showed “[njo couplets or tachycardia beats” but Mr. McKinley reported “some sensations of rapid heart beating.” Eventually, the drug Norpace was prescribed (400 mg. per dose).
On January 6, 1991, Mr. McKinley was ordered by his supervisor, Mr. Robert Cur-rence, to operate a television camera moments before a broadcast was scheduled to begin. Mr. Currence yelled at Mr. McKinley, telling him that the schedule had been changed, and questioned why he did not review his schedule. After the broadcast, Mr. Currence continued to reprimand Mr. McKinley who became fearful of a physical assault. The following day Mr. McKinley arrived late to work and Mr. Currence had already left for the evening. Therefore, there was no contact between the two men. However, co-workers advised Mr. McKinley that Mr. Currence was angered and irritated by his tardiness.
Mr. McKinley did not work on January 8, 1991, but called his office for an unrelated *1379matter. He did not speak with Mr. Cur-rence, but someone advised him that Mr. Currence’s criticism continued. On January 9,1991, Mr. McKinley filed a union grievance against Mr. Currence, and informed his employer that he did not intend to return to work until the matter was resolved. This was his first complaint against Mr. Currence. On January 10, 1991, Mr. McKinley received a call from Mr. Michael Maher, a member of the station’s management, notifying him that the complaint was under investigation and that he was expected to return to work. Mr. McKinley did not speak with Mr. Currence before or after Mr. Maher’s call. Some time after the phone call Mr. McKinley ate dinner, and attended church with his family.
Later that evening while en route to work via Interstate 270 in Maryland, Mi*. McKinley experienced lightheadedness, palpitations and dizziness. He pulled over to the side of the road until the symptoms abated. As he resumed his trip, his lightheadedness and palpitations recurred. He stopped at a gas station. An ambulance was called, and he was transported to Frederick Memorial Hospital where he was evaluated and treated. At the time of his attack, Mr. McKinley said he believed that his death was imminent.
Dr. Edward Riuli saw Mr. McKinley at Frederick Memorial on January 10 after his experience on 1-270. He found a regular heart beat and heard a “systolic murmur ... at right external border.” His assessment in part was “[p]alpitations, need to rule out recurrent ventricular tachycardia.” He noted that “[Mr. McKinley] is uncertain whether [his reported palpitations were] actually true arrhythmias as he has had in the past, versus stress related palpitations.” When Mr. McKinley saw his treating physician, Dr. Jeffrey Cowen after the highway incident, Dr. Cowen noted no arrhythmias. Nonetheless, Dr. Cowen equipped Mr. McKinley with a holter monitor on January 17 and 18, 1991. According to Dr. Cowen, the results of the holter test were “extremely benign. He had occasional PVCs, nothing worse.” Dr. Cow-en referred Mr. McKinley to a psychiatrist, Dr. Jeffrey Mendell. Mr. McKinley also was examined by doctors at NIH on January 30 and 31, 1991. Notations on those days by NIH doctors indicate that Mr. McKinley was “concerned [about] recent episode of palpitations and near syncope” and that “while driving” he reported “episodes of palpitations with dizziness.” There is no reference to his place of employment or Mr. Currence. On February 25, 1991, Dr. Anne B. Cetnarow-ski-Cropp of NIH’s Cardiology Branch, wrote, “Robert B. McKinley is a patient of the National Institutes of Health. After his physical examination on January 30th, I recommended to Mr. McKinley that he should be admitted to the Clinical Center for evaluation of an investigational medication for his medical condition.” Mr. McKinley was scheduled to be readmitted to NIH on March 17, 1991, for a two week period to participate in tests involving the medication.1
Mr. McKinley did not work between January 10 and February 15, as scheduled. Beginning around February 15, 1991, he went on a scheduled paternity leave for three months in connection with the birth of his new child, and did not return to work until May 16, 1991. On May 13, 1991, Dr. Lameh Fananapazir, head of the Eleetrophysiology Laboratory, Cardiology Branch, at NIH responded to a letter from Mr. McKinley which apparently inquired about his return to work. She wrote, “[i]n response to your letter of May 10, addressed to Dr. Cropp, this is to confirm that we believe you should be able to return to your employment, provided that you avoid heavy physical exertion or extraordinary emotional stress.”
Mr. McKinley went to work on May 16, 1991, and met with officials at the television station. Mr. Currence did not work on that day, and had previously given up his position as a supervisor. After his meeting with station officials, another employee, Mr. John Hanson, reportedly told Mr. McKinley that Mr. Currence said “he couldn’t wait to see me so he could put the fear of God into me and hoped I would die.”2 The record does *1380not reveal any medical treatment on May 16. On June 6,1991, Dr. Cowen saw Mr. McKinley and noted, “[h]e has had no palpitations, dizziness, syncope, chest discomfort [or] shortness of breath.... Patient appears to be doing quite well.” The record before us reveals no other visit to Dr. Cowen by Mr. McKinley.
Mr. McKinley filed a claim for benefits under the District of Columbia Workers Compensation Act, seeking an award for temporary total disability under the Act, from January 10, 1991 to April 1992. In his answers to interrogatories, he claimed as his injuries, “a run of ventricular tachycardia, a cardiac dysfunction” and “post traumatic stress, an emotional injury.” A full eviden-tiary hearing was held by the agency on November 19, and December 2, 1991. The hearing examiner articulated the following issues:
1. Whether claimant sustained an injury which arose out of and in the course of his employment.
2. The nature and extent of claimant’s current disability, if any.
3. Whether claimant’s current disability is causally related to his employment.
4. Whether claimant voluntarily limited his income.
Mr. McKinley was the only witness to testify in his behalf at the hearing. He provided an account of his experiences with Mr. Cur-rence, the episode of January 10, 1991, the history of his heart condition, his psychotherapy treatment, and other matters. The company presented testimony by Mr. James Gilmore, Jr., a supervisor and Mr. John Tol-lefson, Vice President for Operations & Engineering at WJLA-TV. Mr. Gilmore gave his impressions of Mr. McKinley, and described the interaction between Mr. Cur-rence and Mr. McKinley. He indicated that Mr. Currenee had a “harsh” management style and often was called “Little Hitler.” Mr. Gilmore said he “may have once” witnessed a personal confrontation between Mr. Currenee and Mr. McKinley when Mr. McKinley reported to work late. According to him, in that confrontation Mr. Currenee “just rode [Mr. McKinley] for about the best part of an hour or so.” When asked whether Mr. McKinley was “a sensitive individual,” Mr. Gilmore responded, “I think that was basically because of his condition. If something was going wrong, most of us would be able to handle that amount of stress; whereby with him, he wouldn’t exactly go to pieces, but it would bother him as the day wore on.”
Mr. Tollefson, the Vice President for Operations & Engineering at WJLA-TV investigated Mr. McKinley’s accusations of harassment against Mr. Currenee. These accusations were detailed in a letter dated January 10, 1991.3 According to Mr. Tollef-son’s testimony, workers described Mr. Cur-rence as a “strong supervisor.” One employee said “he tended to act at times like a little drill sergeant, trying to keep all the troops together and doing what they are supposed to be doing_” Mr. Tollefson also heard Mr. Currenee referred to as “Little Hitler.” However, Mr. Tollefson “could not substantiate the charges of harassment that Mr. McKinley had in his letter, ... [but] did, however, ... find that some of Mr. Cur-rence’s actions were not proper, and he was issued a letter of reprimand.” On cross-examination, Mr. Tollefson explained, “I had found that some of Mr. Currence’s actions not related to Mr. McKinley were inappropriate which led to his letter of reprimand. ...” After he received the letter of reprimand, Mr. Currenee asked to be relieved of his supervisory duties. In August 1991, Mr. Tollefson heard allegations about some threats Mr. Currenee had made, not to Mr. McKinley, but about Mr. McKinley. He investigated and found that Mr. Currenee “had acted inappropriately.” Mr. Currenee was suspended without pay, pending a discharge.
Medical reports were received into evidence, as well as deposition testimony from Dr. Cowen, and Dr. Jeffrey Mendell, a psychiatrist who treated Mr. McKinley at the recommendation of Dr. Cowen. During his deposition on October 30, 1991, Dr. Cowen *1381expressed the opinion that on January 10, 1991, Mr. McKinley “had an episode of ventricular tachycardia that spontaneously converted to normal sinus rhythm, normal sinus rhythm being the normal rhythm.” When asked what caused the condition, Dr. Cowen identified Mr. McKinley’s stress level as one contributory factor and his “hypertrophic obstructive cardiomyopathy” as the other. When asked whether he had “encountered situations where patients or people suffered V-tach without any unusual stress,” Dr. Cow-en said “yes.” In response to the question, “[i]s it possible it could have happened in Mr. McKinley’s case,” Dr. Cowen stated, “[i]t’s possible.” Dr. Cowen also asserted, “[t]he cause for this gentleman to have ventricular tachycardia is his underlying heart disease that makes him susceptible. Precipitating factors are varied and multiple, and with many contributing causes occurring at one point, and the rhythm disturbance is initiated. Of those causes stress appears to be one of them.” He identified other causes as “[t]he electrical milieu of your automatic nervous system[,][p]harmacological agents ... in the body at the time[,][a]lcohol, disturbances in electrolytes, oxygenation in an individual with disease who has asthma, or pneumonia whose oxygen levels become low_” In response to the question, “[b]ut we have no objective way of knowing which of those several items you just mentioned may have been a particular trigger in this case,” Dr. Cowen said, “[tjhere’s no objective way to tell.” He also acknowledged that if Mr. McKinley did not have a heart problem, it was “very unlikely” that stress would have caused the V-tach. Dr. Cowen indicated that Mr. McKinley was taking the drug Norpace on January 10, 1991, and that “nobody measured” whether he had alcohol in his system.4
The deposition of Dr. Mendell took place on November 4, 1991. He began treating Mr. McKinley on February 14,1991. Initially, he diagnosed Mr. McKinley as having “an adjustment disorder, ... mixed emotional features.” Later, on May 24, 1991, his diagnosis was changed to “post-traumatic stress disorder.” During his discussion of V-tach, Dr. Mendell said,
Mr. McKinley had been through ventricular tachycardia, and fibrillation, and cardiac arrest twice before. And ... knew what the significance of that was. And ... as he sat in the car at the filling station [on January 10, 1991], he — by his report to me — was thinking that he was going to die. That he was not going to see his child that hadn’t been born yet, and was not going to see his wife again.
Dr. Mendell recounted Mr. McKinley’s two “unsuccessful trials of medication in one afternoon” at NIH “where ventricular tachycardia was induced ... [and Mr. McKinley went] into ventricular fibrillation and cardiac arrest, and was given the electric shocks to restart his heart.” Dr. Mendell performed a “mental status examination” on Mr. McKinley during his February 14, 1991, visit. The examination revealed, inter alia, that Mr. McKinley’s “thought content was focused largely on his fears about his cardiac problems. He stated, T could have died.’ I have a defective feeling, guilty because my son also has the early signs of the same illness.’ ” During one of his early psychotherapy sessions, Mr. McKinley “told [Dr. Mendell] about difficulties with his wife, sexually, fears, anxieties, unable to perform at all.”
Dr. Mendell was asked whether he had “an opinion which you can express, within reasonable psychiatric certainty, as to what caused the condition which you’ve diagnosed as post-traumatic stress disorder?” He responded,
[w]ell, I think the specific stimulus was the episodes on [I-] 270 when he was on his way to work and developed the ventricular tachycardia, which is — I think clearly, was a near death experience, and was certainly interpreted that way by him.
Now, I have no independent information about what happened at work, but clearly the reports that he gives me are that the stress, and what he described as harassment from this supervisor at work, were *1382what led to the stress that led to that episode. And, I mean, his — his associations that induced the post-traumatic symptoms are not cars, filling stations or 270. They’re work, or anything related to the supervisor — well, more than the supervisor. Anything that reminds him of work at all.
Dr. Mendell agreed that post-traumatic stress disorder “is commonly diagnosed in veterans and military combat and in people who have been raped.” However, he considered Mr. McKinley’s situation to be “similar ... [b]ecause it was a near death experience at the time of severe fear or harm.” When asked, “isn’t it true in cases of post-traumatic stress disorder, the stressor is the thing that causes the symptoms of post-traumatic stress disorder to occur ... [and] in this case it’s the episode on [I-] 270,” Dr. Mendell replied, “ty]es.” In reply to the question, “[s]o it’s not WJLA, or ... Mr. Curranee (sic), is that what you’re saying,” Dr. Mendell stated, “[w]ell, what I said is that the incident which triggered the symptoms was the episode on 270. I then reported ... that I have no direct knowledge of what happened at work, but ... I have Mr. McKinley’s report of the stressors which led up to the occurrence, and I do note, not from direct treatment of ventricular tachycardia or this sort of cardiom-yopathy, but from reports of two cardiologists that stress — consistent stress can lead to decompensation of the heart.”
In addition to the depositions of Dr. Cowen and Dr. Mendell, the hearing examiner had written reports from Dr. Brian Schulman, an occupational psychiatrist who examined Mr. McKinley at the employer’s request, and Dr. Lawrence Brain of the Metropolitan Psychiatric Group who examined Mr. McKinley at the request of the CNA Insurance Company. On July 8,1991, Dr. Schulman wrote,
[Mr. McKinley’s] preexistent cardiac condition is a significant medical problem which is obviously unrelated to any conditions of his employment. Further, although he states he had been asymptomatic since the diagnosis of this condition five years ago, that is not the case. He in fact had an adverse response to [the drug] Tenormin which necessitated emergency treatment and hospitalization shortly after the diagnosis of this condition.
Thus, the employee’s contention that the totality of his cardiac problem and the causality for the acute episode is attributable to emotional sequela of the incident of January 7, 1991 is unsubstantiated by medical fact. This is a condition [that] will show a nonspecific response to any type of adrenergic or emotional aggravation.
The substantive medical facts indicate the preexistent presence of idiopathic, hyper-trophic cardiomyopathy which is a congenital condition. Although the employee denies previous symptoms, the acute episode is fully consistent with the natural pathogenesis of this condition, i.e., adrenergic (emotional), stimulation increasing the cardiac output, and in the face of the congenital outflow obstruction, causing symptoms of dizziness, shortness of breath and possibly tachycardia.
Dr. Brain stated in a letter of November 13, 1991,
I do not believe the event described [by] Mr. McKinley, attributable to Mr. Cur-rence, can in any way be considered of the severity necessary as defined by this condition of Post Traumatic Stress Disorder. By contrast, however, it is clear that the event of ventricular tachycardia, some two days later, had a profoundly disturbing effect on Mr. McKinley in that he believed he was “about to die” and that further he was seeking to be “close to my wife.” This is more the traumatic event that has precipitated in him panicky feelings with an Anxiety Disorder and associated panic fearing that almost any circumstance including sex will precipitate the onset of ventricular tachycardia and therefore his demise. Clearly, this is for any person a stressor and is a natural consequence of the medical condition of idiopathic car-diomyopathy. It is clear that the preexisting medical illness in no way correlated to conditions of employment. This situation was further complicated by the fact that Mr. McKinley has in the past experienced two episodes of cardiac arrest which required electrical defibrillation and also may *1383be the precipitants to the anxiety disorder he now experiences.
The hearing examiner issued a decision on June 23, 1995, denying Mr. McKinley’s claim for temporary total disability benefits, because his injury did not arise out of and in the course of his employment. Mr. McKinley filed an application for review. In his application he stated, inter alia, “On June 23, 1995, the Hearing Examiner found that neither Mr. McKinley’s attack of ventricular tachycardia nor his resultant psychiatric disorder arose out of and in the course of his employment. Mr. McKinley applied for review of that decision.”5
ANALYSIS
Mr. McKinley contends that his injury arose out of and in the course of his employment. He claims that the hearing examiner’s decision is not supported by substantial evidence on the record. “In considering petitioner’s argument that the [agency] decision is not supported by reliable, probative, and substantial evidence in the record, see D.C.Code §§ 1-1509(e), -1510(a)(3)(E) (1992 Repl.), we begin with the premise that the agency’s decision ‘is presumed to be correct, so that the burden of demonstrating error is on the appellant or petitioner who challenges the decision.’ ” Robinson v. Smith, 683 A.2d 481, 487 (D.C.1996) (quoting Cohen v. Rental Housing Comm’n, 496 A.2d 603, 605 (D.C.1985)). Furthermore,
[t]he agency must make findings on each material issue of fact; the factual findings must be supported by substantial evidence on the record as a whole; and the agency’s conclusions must flow rationally from those findings and comport with the applicable law. Our function is to ascertain whether the inferences drawn by the administrative agency are within the reasonable boundaries prescribed by the facts.... Factual findings supported by substantial evidence on the record as a whole are binding on the reviewing court, although this court may have reached a different result based on an independent review of the record.
Id. (quoting Williamson v. District of Columbia Bd. of Dentistry, 647 A.2d 389, 394 (D.C.1994)).
There is a presumption of compensability under the Workers’ Compensation Act.6 Spartin v. District of Columbia Department of Employment Servs., 584 A.2d 564, 572 (D.C.1990); see also D.C.Code § 36-321. However, the presumption may be overcome. The “general rule [is] that the occurrence of employee injuries sustained off the work premises, while enroute to or from work, do not fall within the category of injuries ‘in the course of employment.’” Grayson v. District of Columbia Department of Employment Servs., 516 A.2d 909, 911 (D.C.1986) (referencing 1 Lakson, The Law of Workmen’s Compensation § 15.00 (1984)). “An *1384injury arises out of the employment if it would not have occurred but for the fact that conditions and obligations of the employment placed claimant in a position where he was injured.” Id. (quoting 1 LARSON, supra, § 6.50 (emphasis in original)). The hearing examiner determined that,
[i]n the instant case, claimant’s quarrel with Mr. Currence occurred on January 6th. His attack of tachycardia occurred on January 10th on an interstate located in Maryland. There was evidence that the hostility had subsided: claimant had had no contact with Mr. Currence after January 6th, he had filed a grievance, a recognized outlet for disagreements with management, and been informed that it would be investigated. Further, before he went to work on January 10th, he had dinner with his family and went to church. There were no facts weighing toward a finding of work-relatedness.... Wherefore, I determined that claimant’s ventricular tachycardia did not arise out of and in the course of his employment. As the tachycardia was not work-related, any psychological condition attributable thereto was not work-related.
In concluding that Mr. McKinley’s injury was not work-related, the hearing examiner discussed and rejected Mr. McKinley’s reliance on Austin v. Eichberg Constr., H & AS No. 88-311, OWC No. 137466 (February 16, 1990). According to the hearing examiner, that ease involved an “assault [between two employees] which took place a short distance from the worksite a short time after [a] quarrel” about work duties which led to the termination of one of the employees. The hearing examiner distinguished Mr. McKinley’s case from Austin because “[t]here were no facts weighing toward a finding of work-relatedness .... ” In particular, the hearing examiner found that,
Mr. McKinley’s quarrel with Mr. Currence occurred on January 6th. His attack of tachycardia occurred on January 10th on an interstate located in Maryland. There was evidence that the hostility had subsided: claimant had had no contact with Mr. Currence after January 6th, he had filed a grievance, a recognized outlet for disagreements with management, and been informed that it would be investigated. Further, before he went to work on January 10th, he had dinner with his family and went to church.
In addition, unlike Austin, Mr. Currence was not present when the claimed injury occurred outside the WJLA-TV worksite, and there was no assault. Indeed, Mr. Tollefson testified that his investigation could not substantiate Mr. McKinley’s claim that Mr. Currence had harassed him at the television station.
Furthermore, Dr. Schulman stated, “the employee’s contention that the totality of his cardiac problem and the causality for the acute episode is attributable to emotional sequela of the incident of January 7, 1991 is unsubstantiated by medical fact.” Moreover, in essence, Dr. Brain identifies the real stressor in Mr. McKinley’s life and on January 10, 1991, as his fear of dying because of a possible V-tach. As Dr. Brain put it,
it is clear that the event of ventricular tachycardia ... had a profoundly disturbing effect on Mr. McKinley in that he believed he was “about to die” and that further he was seeking to be “close to [his] wife.” This is more the traumatic event that has precipitated in him panicky feelings with an Anxiety Disorder and associated panic fearing that almost any circumstance including sex will precipitate the onset of ventricular tachycardia and therefore his demise. Clearly, this is for any person a stressor and is a natural consequence of the medical condition of cardiomyopathy.
In addition, Dr. Cowen’s testimony does not lend unequivocal support for Mr. McKinley’s theory that work-related stress triggered his V-tach on January 10, 1991.7 Dr. Cowen *1385identified several factors that can cause Y-tach. He admitted that “[t]here’s no objective way to tell” which of the several factors triggered Mr. McKinley’s V-tach on January 10, 1991. He also asserted, “[t]he cause for this gentleman to have ventricular tachycardia is his underlying heart disease that makes him susceptible,” and acknowledged, it was “very unlikely” that stress would have caused V-tach if Mr. McKinley did not have a heart problem. Moreover, the record reveals that when he was treated at Frederick Memorial Hospital on January 10, 1991, Mr. McKinley told the doctors that he was “uncertain whether [his reported palpitations were] actually true arrhythmias as he had in the past, versus stress related palpitations.” And, even Dr. Mendell, Mr. McKinley’s psychiatrist, mentioned his “ventricular tachycardia, and fibrillation, and cardiac arrest” twice at NIH in 1986 as associated with his fear of dying due to a V-tach. When Dr. Mendell performed a “mental status examination” on Mr. McKinley on February 14, 1991, it revealed “thought content ... focused largely on his fears about his cardiac problems,” a belief that “I could have died” [on January 10, 1991], and a “defective feeling, guilty because [his] son also had the early signs of the same illness.” Dr. Mendell candidly admitted that he had “no direct knowledge” or “independent information about what happened at [Mr. McKinley’s] work [site].” In contrast, Mr. Tollefson investigated Mr. McKinley’s accusations of harassment against Mr. Currence and was unable to substantiate them. Mr. Gilmore testified that “[i]f something was going wrong [at the television station], most of us would be able to handle that amount of stress; whereby with him, he wouldn’t exactly go to pieces, but it would bother him as the day wore on.”8 Accordingly, there was substantial evidence in the record to support the hearing examiner’s conclusion that workplace stress did not trigger Mr. McKinley’s V-tach on January 10,1991.
The hearing examiner also addressed Mr. McKinley’s claim “that his psychological condition (injury) was due to the actions of Mr. Currence and that any mention of the employer in any form upsets him for ‘up to two hours or longer.’ ” There is substantial evidence in the record to support the hearing examiner’s finding that, “[n]one of the doctors ... named the etiology as claimant’s work or work environment.” As indicated previously, both Dr. Schulman and Dr. Brain determined that Mr. McKinley’s claimed injuries were not related to his employment. Dr. Brain connected Mr. McKinley’s anxiety disorder to the “two episodes of cardiac arrest [at NIH in 1986] which required electrical defibrillation.” Dr. Brain specifically disagreed with Dr. Mendell’s diagnosis of post traumatic stress disorder, saying, “[t]he diagnostic picture that emerges is of a man with significant anxiety disorder with features of a panic disorder. However, ... I do not concur with the conclusions of Dr. Mendell that this represents Post Traumatic Stress Disor-der_ [W]hile Mr. McKinley did suffer some harassment at the hands of his supervisor this was a pattern of behavior which he was exposed to over an extended period of time and for which he has shown no prior significant adverse response_ [Mr. *1386McKinley’s Anxiety Disorder with panic] is not causally related to conditions of employment.” Dr. Mendell, Mr. McKinley’s psychiatrist also noted that Mr. McKinley’s “thought content was focused largely on his fears about his cardiac problems.” Accordingly, there is substantial evidence to support the hearing examiner’s conclusion that Mr. McKinley’s psychological disorder was not caused by his work environment.
Thus, on the record before us, we cannot say that DOES’ findings regarding whether Mr. McKinley’s injury arose out of and in the course of his employment are unsupported by substantial evidence, or that DOES’ interpretation of its own law or its Austin decision is unreasonable or in error. There is substantial evidence in the record to support the conclusion that neither Mr. McKinley’s V-tach on January 10, 1991, nor his psychological disorder was caused by workplace stress traceable to his problems with Mr. Currenee. As we said in Robinson, “[p]articularly in light of the hearing examiner’s unique position to assess the credibility of petitioner and the other witnesses ... we cannot say that the evidence submitted by petitioner renders the hearing examiner’s finding to be unsupported by substantial evidence in the record as a whole- ‘[A]n agency, as a finder of fact, may credit the evidence upon which it relies to the detriment of conflicting evidence, and [generally] need not explain why it favored the evidence on one side over that of the other.’ ” 683 A.2d at 488 (citations omitted). In short, “[fjactual findings supported by substantial evidence on the record as a whole are binding on the reviewing court,” even if it “may have reached a different result based on an independent review of the record.” Id. at 487. Our task is not to substitute our judgment for that of the agency.
Accordingly, for the foregoing reasons, we affirm the agency’s judgment.
Affirmed.
. Mr. McKinley elected not to participate in the investigational study.
. The DOES hearing examiner found only that Mr. McKinley “returned to work on May 16, 1991, but on hearing from a co-worker that Mr. *1380Currenee wanted to see him, ... became upset and left.”
. Mr. McKinley testified that he wrote the letter on January 9, 1991.
. During his testimony at his hearing, Mr. McKinley admitted "I had alcohol problems.” He also acknowledged that he had been arrested and convicted for driving under the influence or driving while intoxicated. Furthermore, he admitted telling Dr. Mendell "about how [his wife] would look in the file cabinet drawers or whatever to see if I had alcohol hidden."
. Mr. McKinley identifies the issue presented in this matter as "[wjhether the Hearing Examiner erred in finding that [his] injury did not arise out of and in the course of his employment?” In his claim he identified his injury as “a run of ventricular tachycardia, a cardiac dysfunction” and "post traumatic stress, an emotional injury.” Furthermore he states in his Brief at p. 8:
The record evidence establishes without doubt that the psychiatric condition from which Mr. McKinley suffers was either caused or made symptomatic by the January 10, 1991 incident on which this workers' compensation claim is based. Therefore, if the near death experience, the attack of ventricular tachycardia, is a compensable work related incident, there can be no dispute that the resultant emotional or psychiatric condition is work related.
. During his discussion of the "presumption of compensability,” Judge Ferren relies on Professor Larson in emphasizing the distinction between medical and legal causation, and faults the majority for failing to discuss medical causation with respect to "exertion” in "heart attack” cases. Neither party presented arguments which distinguished between medical and legal causation. However, the discussion of both medical and legal causation is implicit in the majority’s opinion. The majority does not approach the theoretical issue of "usual exposure or exertion” in “heart attack” cases, in the same way as Professor Larson does in his extensive treatise, especially in § 38.83(a), and upon which Judge Ferren relies for his analysis. Rather, to determine whether the hearing examiner's decision is based upon substantial evidence, the majority examines the specific facts of Mr. McKinley’s case; the medical opinions of Doctors Cowen, Mendell, Brain, Schulman and others concerning Mr. McKinley’s specific medical (physical and emotional) problems; and the lay testimony introduced during the hearing on Mr. McKinley’s claim for compensation.
. DOES previously has adopted an objective test for determining whether emotional injury is caused by job stress. "[I]n order for a claimant to establish that an emotional injury arises out of the mental stress or mental stimulus of employment, the claimant must show that the actual conditions of employment, as determined by an objective standard and not merely the claimant’s subjective perception of his working conditions, were the cause of his emotional injury. The objective standard is satisfied where the claimant shows that the actual working conditions could *1385have caused similar emotional injury in a person who was not significantly predisposed to such injury.” Spartin, supra, 584 A.2d at 568 (quoting Dailey v. 3M Co., H & AS No. 85-259 (Final Compensation Order May 19, 1988)).
. In Spartin, supra, we pointed out that "Professor Larson advocates an 'objective' standard [for mental stress cases:] 'in order for non-traumatically caused mental injury to be compensable in a workmen’s compensation case, the injury must have resulted from a situation of greater dimensions than the day-to-day mental stress and tensions which all employees must experience.’ ” 584 A.2d at 569 (quoting 1B Larson, supra, § 42.23(b) at 7-669 (other citation omitted)). As we also recognized in Spartin, "work related stressful conditions must be a major contributing cause of the [underlying] disorder, ruling out non-job related sources of stress." Id. n. 7 (referencing McGarrah v. State Accident Ins. Fund, 59 Or.App. 448, 651 P.2d 153 (1982), aff'd, 296 Or. 145, 675 P.2d 159 (1983)). Other than his own subjective testimony, Mr. McKinley presented no evidence to support his theory of workplace stress as the cause of his V-tach episode on January 10, 1991. Both Dr. Mendell and Dr. Cowen relied on his account of stress at the workplace in formulating their opinions. Indeed, Dr. Mendell made it quite clear that he had no direct and independent information concerning what had happened at the television station. In contrast, the employer presented the testimony of Mr. Gilmore and Mr. Tollefson.